was developed in the late 1950's and early 1960's by the US Government
To propel a spacecraft
by exploding atomic bombs
Theodore Tyler and Freeman Dyson
were two of the prominent men behind the project when it was brought to the Advanced Research Projects Agency ( ARPA
) in 1958.
The most common incarnation
called for a battleship
-type space vehicle mounted on top of a large, curved metal plate. Bombs would be dropped out of a slot in the plate followed closely by solid-fuel discs. The bombs would then be detonated at roughly 200 feet behind the plate: the discs would vapourise and the resulting plasma
pushed against the plate, driving the Orion.
In this way, the craft would operate in a pulsed
mode instead of a continuous
one. The advantage to this is the same as a car engine: although the peak temperature is far above the melting point
of the surrounding chamber
or plate, the metal remains intact because the peak temperature is reached only very briefly in the combustion/ignition cycle. Research on the type of metal which could feasibly be used pointed towards either aluminium
The Orion ships designed by Dyson were massive things compared to the contemporary Apollo craft: capable of carrying a crew of 150, with a lift-off mass of 10,000 tons. On takeoff, they would detonate a 0.1 kiloton bomb every second. The rate of denotation would slow, while the yield would increase as the Orion accelerated, eventually reaching its cruising rate of one 20 kiloton bomb every ten seconds.
Unfortunatly, the signing of the Nuclear Test Ban Treaty in 1963 mostly put an end to Orion, since it would make any flights illegal under the terms of the treaty.
More recent studies into Orion have shown that, surprisingly, it could have worked quite well. For an outlay of roughly the same amount as the entire Apollo project, Orion could have been made feasible.